Conventionally, in an image forming apparatus using an electrophotographic image forming process, a photosensitive drum and process parts actable on the photosensitive drum are unfixed into a cartridge. Further, a process cartridge type in which this cartridge is detachably mountable to an apparatus main assembly of the image forming apparatus is employed.
According to this process cartridge type, maintenance of the image forming apparatus can be performed by a user himself (herself). As a result, an operationality can be improved remarkably and the process cartridge type is widely used in image forming apparatuses.
Japanese Patent No. 4464435 discloses a color electrophotographic image forming apparatus in which a plurality of process cartridges are arranged in a line. Here, in the process cartridge, a drum unit including the photosensitive drum and a developing unit including a developing roller are connected rotatably by a swing center. Further, the photosensitive drum is provided with a drum coupling in one end side with respect to an axial direction of the photosensitive drum. Further, when the process cartridge is mounted in the apparatus main assembly, the drum coupling engages with a main assembly(-side) coupling provided in the apparatus main assembly, so that a first driving force is transmitted.
Further, the developing roller is provided with an Oldham coupling which is a shaft coupling member in one end side with respect to an axial direction of the developing roller. The Oldham coupling engages with a main assembly(-side) drive transmitting member, and is constituted by a driving-side engaging portion provided movably in a direction crossing an axis of the developing roller, a follower-side engaging portion fixed to the developing roller, and an intermediary engaging portion provided between the follower-side engaging portion and the follower-side engaging portion. Further, when the process cartridge is mounted in the apparatus main assembly, the driving-side engaging portion engages with a main assembly(-side) developing (means) coupling provided in the apparatus main assembly, so that a second driving force is transmitted. That is, drive transmission from the apparatus main assembly to the process cartridge is performed at independent two positions.
In the process cartridge as described above, independent drive transmission is performed on an axis of the photosensitive drum and an axis of the developing roller. In this way, in the case where the cartridge of the photosensitive drum and the coupling of the developing roller are in a relationship in which these couplings are adjacent to each other, an interval between the drive transmitting member for the photosensitive drum and the drive transmitting member for the developing roller narrows. As a result, a degree of flexibility in constitution of the apparatus main assembly or the process cartridge narrows.